First things first, what does it do? Essentially Chirp lets people share links via sound. If you take a photo for example, Chirp stores the photo in the Cloud and creates a ‘chirp’ – a sequence of 20 notes – which can be understood as a link by any device with the app. So you could send a photo from one smart phone to any number of devices within hearing distance.

But for sound artist Matthew Herbert, the most interesting thing about Chirp is how it affects the way we think about music.

‘I think Chirp changes everything’, he explains. ‘Up to now, melody has just been based on an emotion or it’s been a metaphor. But now melody can transmit data as well and I think that’s a really profound shift in what music is. If a singer could sing the exact notes at 170 beats per minute they’d be able to sing you a PDF, which is a pretty extraordinary shift in what music can do.’

The potential uses for the app are far-reaching. Once you can transmit data between smart phones via sound, why shouldn’t everything that makes a sound broadcast information? You can see why this forward-looking app might have attracted the interest of Herbert, whose new opera is inspired by the story of one of the most ambitious men in Western art – Faust.

‘The great thing about Chirp is the broadcast mechanism, so you can broadcast these little melodies out into a public space and, if they’ve got the app open on their phone, they can receive it. So it’s a very exciting way of breaking the fourth wall and allowing the audience to get extra information, extra images, extra experience.’

Which is, in fact, how the app will be used during performances of The Crackle. Audience members will be encouraged to leave their phones on for the evening (something which Herbert admits feels ‘quite transgressive’) and, if they wish, interact with the performance via the app.

‘Phones are so ubiquitous in our lives – I leave my phone on all the time on silent. And if you’re stuck in a dark room for four hours at the theatre and you’ve hired a babysitter you want to check that your kids are ok. So most people have their phones on. We have to find a new way of listening in the theatre, so that if a phone goes off in the most crucial part, we don’t get frustrated by it.’

So if you’re planning to come along, why not download the app – available from the App Store and on Google Play – onto your smartphone before the performance?